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How To Assess Picture And Sound Quality


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#26 Owen

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Posted 25 June 2009 - 07:33 AM

Power supply limitations have been blamed for the phenomenon; it may be due to voltage drop or current limits within the panelís internal circuits rather than poor main power supply regulation, this would result in poor regulation at the pixel level but would obviously not be observable on the main power supply rails.
One thing is certain, ALL Plasmas from the most expensive Pioneer and Panasonic models to the cheapies suffer from very significant negative dynamic contrast. Peak output on high average picture level scenes is always much lower than peak output on low average picture level scenes.

#27 DrP

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Posted 25 June 2009 - 08:29 AM

That may well be the case. Plasma panels are particularly sensitive to over voltage conditions (which could happen if the brightness was allowed to jiggle the voltages up and down rapidly) - even a moderate overvoltage situation can result in all the panel drivers being killed in an instant* (panel replacement is the only option when this happens) so the PSUs do have to be fairly well designed and behaved. There are instances that have appeared on this very forum where panels have died due to overvoltage.



*Before PDPs became popular for watching TV I had the job of replacing a panel that had failed in some commercial equipment. Unfortunately an intermittent fault in a hidden secondary power supply killed the replacement in a couple of weeks time.... It would have been an expensive repair job but fortunately the panel vendor - starts with Tos.... - came to the party and agreed to replace it FOC under warranty.

#28 Recusant

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Posted 27 June 2009 - 01:51 PM

Can overvoltage be protected against? A surge protector for example?

#29 alanh

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Posted 27 June 2009 - 02:14 PM

Recusant,
This is not relevant to this strand.
This topic has been covered many times.
Please use this site's search using surge and alanh as a poster's name.

AlanH

#30 DrP

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Posted 27 June 2009 - 05:54 PM

Perhaps if you improve your comprehension a tad, AlanH, you'll come to realise that Recusant was referring to overvoltage conditions to which plasma panels are sensitive as mentioned above, not mains borne issues. Searching for your regurgitation of what others have posted WRT mains filtering is completely irrelevant in this instance.

Recusant, there is no protection for the problem I mentioned aside from decent design and construction of the set in the first place. A panel being kiled due to it is a pretty rare thing these days anyway.

#31 alanh

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Posted 27 June 2009 - 08:16 PM

DrP,
LCDs monitor the average picture levels and if they remain for enouth time low the brightness of the back lighting is reduced. you can see the brightness of small white area of white goes darker. This is part of screen saving.

AlanH

#32 Owen

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Posted 27 June 2009 - 11:20 PM

WTF ?????

#33 DrP

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Posted 28 June 2009 - 06:53 AM

WTF ?????

A question that is oft asked.

#34 DrP

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Posted 28 June 2009 - 07:03 AM

DrP,
LCDs monitor the average picture levels and if they remain for enouth time low the brightness of the back lighting is reduced. you can see the brightness of small white area of white goes darker. This is part of screen saving.

AlanH

I'll attempt to untangle this latest post of alanh's and perhaps he'll learn something at the same time - however there's none so deaf as those that will not hear.

The reason some LCDs dynamically vary the backlight WRT picture content is to give the impression of a greater range of brilliance capabilities more in line with what one experiences with CRTs and plasma panels. It is also an attempt to hide back light bleed through the LCD (this is not 'torchlighting' from the edges). It does nothing for the longevity of the backlight lamp, it does nothing for the longevity of the LCD itself and it is certainly not a 'screen saver'.

'Screen savers' came about to prevent image 'burn' on CRTs when used with long term display of high contrast static images. While it is possible to damage an LCD in this way the time the high contrast static image has to remain displayed is extremely long and could only ever happen under artificial use (ie, image shown 24 x 7 - the set not being used for TV viewing at all).

As for the whole LCDs changing the backlight levels.... you know, I think this was bought up earlier in this thread. As yes, here we go. Did you miss this post, alanh?

Some LCD sets deliberately alter the backlight level in response to overall picture conditions but that is by design.


Edited by DrP, 28 June 2009 - 08:02 AM.


#35 anon_

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Posted 04 July 2009 - 03:08 PM

Anyone know if there is any point in upgrading to the Bu-Ray edition of DVE. I have had the SD edition for awhile.

Is it worth it to calibrate a new projector and system?

#36 alanh

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Posted 04 July 2009 - 06:23 PM

anon_
If you are only going to check the setting of brightness and contrast there is no point. However if you wish to check the colour rendition and sharpness of image there is. This is because a DVD is limited to 720 x 576 images instead of 1920 x 1080. Also the colours used for HD images are different to those in SD.

AlanH

#37 DrP

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Posted 04 July 2009 - 06:59 PM

Also the colours used for HD images are different to those in SD.

Oh no! Not again. :wacko:

#38 anon_

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Posted 04 July 2009 - 07:37 PM

Alrighty, cheers.

#39 Owen

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Posted 05 July 2009 - 05:50 PM

SD and HD use different color space, nice simple explanation here:

http://www.glennchan...color-space.htm

#40 DrP

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Posted 05 July 2009 - 05:59 PM

You probably missed the thread concerning colour matrixes etc.

#41 alanh

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Posted 05 July 2009 - 08:08 PM

DrP,
So when are you going to admit that what I have been saying about colour primaries and matrixes is correct?

AlanH

#42 DrP

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Posted 05 July 2009 - 08:48 PM

alanh, you have studiously avoided the question put to you in the other thread. Please explain how a person with a typical consumer grade DVD player selects the wrong colour matrix. While you are at it, please finally admit that HDMI signals the colour matrix used. BTW, HDMI can carry several colour signalling methods including RGB. From your other posts it seems that you believe HDMI can only carry 'YUV' formats. This is incorrect.

There's quite a few other issues that you have failed to answer from that thread (and offshoots) but those two points are a good start.

Looking back at your posts (in these and other threads) you seem to be on a steep learning curve WRT colour matrixes as well as MPEG-2 and MPEG-4 in general. Perhaps you should take some time away from the forum to study and digest the material as you have made some fairly heavy errors regarding them.

Edited by DrP, 05 July 2009 - 09:04 PM.


#43 alanh

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Posted 06 July 2009 - 01:25 AM

DrP,

AlanH 15th June

If you wan to use the matrix for the composite PAL output go for it. Since the BL and HD broadcast or play Y, Pr & Pb and the HDMI is also Y, Pr & Pb why do you need a matrix? The only function for the matrix is to convert from Y, Pr & Pb to RGB. Its been a long time since RGB has been on the outputs of a consumer device.


DrP 16th June

Let me know when you've departed fantasy dream land and make it back to reality and display devices and correct the the error in the above quote. (how can you fit so many errors in such a small space?)


DrP

Not again


Please read today's post from Owen


The only place where there is a matrix is in the camera coder, any studio upconverter and the display. There is no matrix in between the studio and the decoder in the display. So there is no need to know about matrixes in DVD, Blu-ray players, STBs or PVR.

The Camera Coder produces digital levels of the Y, Pr and Pb signals. These levels are unchanged right through to the display via the HDMI cable. Yes HDMI carries Y, Pr & Pb to the display which then converts the output of its memory into RGB. The display can be told which matrix to be used either from the control bits in the data or the number of lines in the active picture. The HDMI connection only has to connect the program source and the display as an error free digital connection that is all.

With regard to using meters, note I did not use any light meters. This is because any variation in the colour of the actual primary colours from the standard colours of red green and blue used in the display will make light meter readings wrong. Radiation meters are only found in R&D labs. The next best thing is to use the comparison from true shades of grey with the display.

AlanH

#44 DrP

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Posted 06 July 2009 - 06:34 AM

Please read today's post from Owen

Yes indeed you should alanh, indeed you should; and while you are at it, go back and re-read my posts and comprehend what I've been saying - repeatedly.

Edited by DrP, 06 July 2009 - 06:35 AM.


#45 :)

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Posted 12 July 2009 - 12:49 PM

~
My suggestion, burn the free AVS HD 709 disk to a DVD-R (read http://www.avsforum....d.php?t=948496)

~

Dennis.


as suggested by Dennis here could perhaps be a freebie option for those, which you can download from avs :)

#46 086

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Posted 27 July 2009 - 10:20 AM

Does anyone know the specs for the blue filters used in these calibration schemes? I have a set of Cibachrome filters (various intensities of cyan, magenta and yellow filters used for printing from slides) and could probably combine a cyan and magenta filter of the same level to make blue.

#47 alanh

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Posted 27 July 2009 - 01:16 PM

086,
What are the specification of the colours of your filters?
Alan

#48 086

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Posted 27 July 2009 - 01:39 PM

What are the specification of the colours of your filters?

Good question. I thought there were details in the box but either there weren't any, or I've lost them. They are however standard enlarger filters and come in:
.05Y, .10Y, .20Y, .30Y, .40Y, .50Y
.05C, .10C, .20C, .30C, .40C, .50C
.05M, .10M, .20M, .30M, .40M, .50M

It probably doesn't matter now as I realised the TV has a Blue-Mode which I ended up using. There may be some people out there that could use the filters.

#49 Owen

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Posted 31 July 2009 - 08:37 PM

Why is this silly thread pinned?

#50 DrP

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Posted 01 August 2009 - 06:28 AM

To highlight the rather large holes in the knowlegde of a forum member whose name that starts with 'a' and warn forum 'newbies' that not everything that is posted by anyone should be taken as gospel?

Edited by DrP, 01 August 2009 - 08:21 AM.